Field of the Invention
The present invention relates to a developing apparatus provided in an electrophotographic or electrostatic-recording image forming apparatus.
Description of the Related Art
Developing apparatuses equipped with a developer container storing a two-component developer including carrier and toner and a developer sleeve, i.e., developer bearing member, bearing the developer and rotating, are used widely as the developing apparatus provided in an electrophotographic image forming apparatus. A developing sleeve rotates while bearing the developer stored in the developer container, and supplies toner to an image bearing member such as a photosensitive drum, to thereby develop an electrostatic latent image on the image bearing member as a toner image. As an example of such developing apparatus, a so-called functionally separated configuration is known, where the inner space of the developer container is divided by a partition into a first chamber for supplying developer to a developer bearing member and a second chamber in which the developer used for developing an image is recovered from the developing sleeve.
Japanese Patent Laid-Open No. 2012-032488 discloses a functionally separated developing apparatus that includes a developing tank in which a first conveyance path, i.e., first chamber, and a second conveyance path, i.e., second chamber, are formed, and a slide member constituting a slope along which developer having fallen from the developing sleeve falls into the second conveyance path. In this developing apparatus, the first conveyance path and the second conveyance path are arranged side by side in a horizontal direction, and separated by a separating wall, i.e., partition wall, extending upward from a bottom portion of the tank. The slide member is disposed above the partition wall, and the developer having fallen from the developing sleeve slides down on the slope of the slide member and is recovered to the second conveyance path.
According to the functionally separated configuration, the developer recovered from the developing sleeve is sequentially added to the developer being conveyed in the second chamber, so that in the second chamber, the developer surface tends to be raised toward the downstream side in the second chamber in the conveyance direction of the developer. Therefore, the agitation of the developer near the surface layer is not easily promoted at the downstream portion of the second chamber. Generally, a conveyance member such as a screw that agitates and conveys the developer by rotation is arranged in the second chamber. The developer positioned above a rotation trajectory of the conveyance member could not be easily drawn to the inner side of the rotation trajectory even when the conveyance member is rotated, and tended to stay in a vicinity of the surface layer.
According to the developing apparatus disclosed in Japanese Patent Laid-Open No. 2012-032488, a communication path, i.e., transfer portion, through which the developer in the second conveyance path is transferred to the first conveyance path, is formed in a downstream part of the partition wall in the conveyance direction of the second conveyance path. Further, a configuration is adopted where a portion of the developer recovered via the slide member (hereinafter referred to as a recovered developer) falls to a position overlapped with the communication path. As a result of this configuration, however, the recovered developer having a low toner density after supplying toner to the image bearing member falls near the communication path having a high developer surface. Therefore, a portion of the recovered developer may move in floating motion on the surface layer of the developer, and flow into the first conveyance path in a state not sufficiently agitated with the surrounding developer. Thus, the developer becoming heterogeneous by the recovered developer may be borne on the developing sleeve and used for developing images, which may cause unevenness of density or other image defects.